This invention concerns a method to form metallic cages for reinforcement purposes and the relative device.
The invention is employed to facilitate, accelerate and simplify the positioning of the stirrups and the longitudinal rods in metallic cages, and also the operations to attach the rods to the stirrups.
The metallic cages as used with the invention are employed as reinforcement in load-bearing structures in reinforced concrete such as beams, pillars, foundations, etc.
Metallic cages used in load-bearing structures in reinforced concrete comprise a plurality of longitudinal rods, normally round pieces, possibly ribbed and/or shaped, with which a plurality of transverse stirrups, distanced lengthwise, are associated.
The stirrups can be of any shape whatsoever, for example polygonal, circular, in a mesh, etc., at least partly closed.
In the state of the art, the metallic cages are assembled manually, for the most part, because, among other reasons, it is difficult to automate the assembly operations; these difficulties derive from the great variety of the structural characteristics of the metallic cages.
The composition of the metallic cage varies both according to the geometry of the load-bearing structure where they are to be used, and also according to the stress to which the structures are subjected.
Therefore, it often happens that metallic cages which are equivalent in size and geometry have to reinforced with a variable number of rods, or with reinforcement rods arranged differently inside the stirrup, or with stirrups having a differentiated interaxis.
This causes considerable operating difficulties for the assembly workers who are obliged to perform continuous measurements before welding, with a high risk of error.
Another considerable problem is the positioning of the longitudinal rods, which can reach lengths of as much as 12 meters and more, inside the stirrups, or inserting the stirrups outside the rods if the rods are already arranged positioned on trestles or other supporting means.
A further considerable problem is to maintain the longitudinal rods and the stirrups in position during the welding and tying operations.
Yet another problem is to ensure the axial alignment of the longitudinal rods.
All these problems become even more important when the stirrups to be assembled are wide, because of the difficulty of positioning and supporting them in an erect position while the cage is: being formed.
There are solutions known to the art which use partly automated machines, or cage-producing machines, which limit the manual operations required for assembling the cage and make the operations for the workers easier.
These machines comprise means to retain and position the longitudinal rods cooperating with movable means to transport and position the stirrups in a controlled manner.
The movable means, as they move parallel to the longitudinal rods, allow the stirrups to be picked up and progressively distributed by the worker along the whole length of the cage.
Although such machines are extremely efficient, they may be too complex, sophisticated and over-sized for requirements, they need heavy investment, equipping operations, complex systems to move and control them, large spaces for manoeuvring, and equipment which requires constant maintenance and constant attention by the workers.
Moreover, in the case of very large metallic cages, the machines are unsuitable to support and stably maintain the stirrups to be assembled in an erect position, especially when the latter are very wide.
Therefore, if on the one hand these machines meet the need of automating the construction of a metallic cage almost completely, on the other hand they have problems of expense, simplicity and practicality, both during construction and during use.
U.S. Pat. No. 5,350,162 describes a device to form metallic cages comprising a plurality of pairs of retaining elements with a vertical development able to be reciprocally separated according to desired values in both a longitudinal and transverse direction, which serve to position the longitudinally separated stirrups in an erect position.
The rods to be attached to the corners of said stirrups are inserted longitudinally inside the stirrups.
This document does not provide in any way to vertically displace the rod support elements with respect to the stationary stirrups, or vice versa, in order to facilitate the positioning and attachment of the rods to the various vertical levels of the stirrups.
Therefore, with this device, to position the rods at the highest levels inside the stirrup, at least two people need to raise one rod at a time, holding it at the end, and take it to the desired level, and a third person has to carry out the attachment operation; otherwise, the same person has to support the rod with one band while at the same time he does the tying operation with the other hand.
It is obvious that this operation not only necessarily requires the intervention of at least two people, but also involves a considerable physical effort and considerable care, with the risk on the one hand of making an unsatisfactory attachment and on the other hand of causing accidents, particularly in the case of very long and heavy rods.
Another disadvantage comes from the fact that, if on the one hand there is no problem of positioning in the case when the rods are attached only in correspondence with the upper inner corners of the rod, on the other hand, in the case when the rods are positioned at one or more intermediate levels in height, a considerable problem is created concerning the accuracy of the positioning.
In this case, which is the more frequent one in the production of metallic cages, the workers are obliged to take reference measurements on the sides of the stirrup according to the design specifications of the cage, and then try to respect these reference measurements while they are supporting long, heavy rods at the ends and tying them.
EP-A-0.376.765 describes the use of identification elements to indicate the position where the stirrups have to be located with respect to the longitudinal rods.
This document does not describe a method or a device to facilitate the formation of a metallic cage.
The present applicants have designed, tested and embodied this invention to overcome the shortcomings of the state of the art with a solution which combines efficiency, practicality, versatility, flexibility and economy, and also to obtain further advantages as will be shown hereinafter.
The purpose of the invention is to provide a device to form metallic cages which will accelerate, simplify and rationalise the operations to position the rods and stirrups, whatever their size, and also the operations of welding or tying in the assembly steps.
The invention also makes possible to vary the interaxis between the stirrups extremely quickly, and to position the longitudinal rods in the correct positions established by the design plans of the cage, without carrying out manual measurements which often cause errors and lead to time being wasted.
The invention uses a plurality of seatings for means to position and retain the stirrups; the seatings are distributed lengthwise along the length of the cage to be formed.
Moreover, the invention includes means to support and position the longitudinal rods of the cage to be assembled; these means are arranged at intervals along the length of the cage.
The seatings for means to position and retain the stirrups are arranged lengthwise with a pre-defined interaxis, either fixed or variable, and cooperate with marker means which identify the position of the stirrups to be inserted according to the design specifications of the cage to be made.
In a first embodiment, the marker means are manual and the workman applies a marker element from time to time in correspondence with the seating where the stirrup is to be inserted.
According to a variant, the marker means are commanded by remote control means and consist of visual indicators which light up in correspondence with the seating where the stirrup is to be inserted.
According to a further variant, when the worker prepares to begin the first cage in a series of identical cages, he inserts the individual stirrups, which causes the light signal to be activated; at the end of the series the light signal is cancelled.
In another embodiment, the marker means consist of a chain, belt, conveyor, etc., which can move lengthwise to the frame of the device, to which a marker element is attached; the chain, belt, conveyor, etc. is stopped from time to time, to arrange the marker element in the position where the stirrup is to be inserted.
In a variant of the invention, the interaxis between the housing seatings is a sub multiple of a range of defined interaxes of the stirrups.
In one embodiment of the invention, the interaxis is 50 mm.
According to a variant, to form cages with stirrups closer together the interaxis is 25 mm.
According to a variant, all the available seatings are occupied by means to position and retain the stirrups, of which only some are used during the formation of the cage; those to be used are identified by the marker means.
In a referential form of this embodiment, the means to position and retain the stirrups are made on profiles arranged between the means to support and position the longitudinal rods.
According to another variant, the means to position and retain the stirrups can be extracted from the relative housing seating and are positioned from time to time in the appropriate seatings identified by the marker means.
According to a further variant, the means to position and retain the stirrups can slide along guides which are longitudinal to the machine and are positioned from time to time according to the marker means.
In this last embodiment, only a limited number of means to position and retain the stirrups are needed compared with the range of interaxes which the stirrups have to assume along the cage.
In one embodiment, the means to position and retain the stirrups consist of a pair of adjacent sections defining a channel to contain the stirrups.
According to the invention, one of the adjacent sections is stationary and one is movable.
According to a variant, the sections are both movable.
During the initial positioning step, the two elements are placed at a distance from each other to allow the stirrups to be inserted easily; the latter are arranged as desired on a substantially vertical plane inside the containing channel.
When the initial positioning has been concluded, the positioning and retaining means are clamped against the stirrup, locking it into the erect position lying on a plane substantially orthogonal to the longitudinal plane of the cage to be formed.
According to a variant, the positioning and retaining means consist of a single angle section, the rear part of which is cone-shaped and serves for positioning.
The means to support and position the longitudinal rods consist of a plurality of transverse arms orthogonal to the axis of the cage and arranged at intervals on a plane substantially parallel to the lower plane on which the cage lies.
According to a first embodiment, the transverse arms, which are interposed between the means to position and retain the stirrups, are movable at least vertically so as to position the longitudinal rods in cooperation with the stirrup at various heights during the attachment steps.
According to a variant, the means to vertically move the transverse arms are associated with means to measure and display the movement.
According to a further variant, there are seatings to guide the longitudinal rods on the transverse arms.
According to another variant, the transverse arms are lined with wear-resistant material.
According to another variant, the transverse arms can be associated with extension elements of the rapid replacement type which allow the longitudinal rods to be positioned and supported in a suitable manner even when the cage has a considerable width.
The extension elements are of different lengths and are used according to the width of the cage to be formed.
According to a variant, the transverse arms are stationary while the means to position and retain the stirrups are movable vertically to obtain the reciprocal positioning in height of the longitudinal rods and the stirrups during the step of forming the cage.
According to the invention, the procedure to form the cage is as follows: first the stirrups are inserted, at an interaxis given by the design specifications, into the relative positioning and retaining means, which means are identified by the marker means.
Then, the transverse arms are slightly raised with respect to the lower plane of the stirrup.
In the case when the arms are stationary, all the stirrups are slightly lowered with respect to the plane defined by the transverse arms.
This relative movement in height of the stirrups and rods facilitates the insertion of the longitudinal rods inside the area defined by the stirrups, and avoids the risk of blockages or of the rods being obstructed.
When all the longitudinal rods have been inserted, the transverse arms are lowered again, or the stirrups are raised, resting all the rods on the side or lower segment of the stirrups.
The longitudinal rods are then all axially aligned lengthwise, using abutment elements arranged in cooperation with one end of the device, advantageously the forward end.
Then, all the longitudinal rods are taken substantially to the highest level of attachment required by the design of the cage, thus making it possible to begin the operations of attaching, welding, tying etc. the rods to the stirrup.
These operations are consequently much simpler, as the longitudinal rods rest on the transverse arms at the desired height with respect to the stirrups.
When the operation to attach the rods in a high position between inside the stirrup is concluded, the, reciprocal position of the stirrups with respect to the rods is varied until all the desired reciprocal positions are obtained, thus allowing the reciprocal attachment to be achieved.
In order to attach one or more longitudinal rods in correspondence with the segment of the stirrup which cooperates with the means to position and retain the stirrups, the cage formed at that point can be partly extracted at the side, freeing said segment of stirrup and enabling the relative longitudinal rod to be attached in said position.
According to a variant, the device has in an adjacent position a base with a sliding plane for a trolley to carry the stirrups or to support a welding machine; the sliding plane may include guide means for the trolley.
According to another variant, on the base there is a longitudinal supporting element to support stirrups which protrude at the side for a large segment of the lateral bulk of the device to form the cage.
According to a further variant, the longitudinal supporting element is movable transversely on the base so as to adapt its position according to the width of the stirrups to be supported.
According to a further variant, the longitudinal supporting element is attached to the base which can be moved in a transverse direction to the frame of the device to form cages.
In a first embodiment, the longitudinal supporting element, or the base, is moved manually.
According to a variant, it is moved by automated means.
The longitudinal supporting element allows the stirrups to be supported securely and therefore to be positioned more stably in their erect position; this is particularly useful when the stirrups tend to fall onto the working plane due to their width, their weight and their vertical arrangement.
According to a variant, the longitudinal supporting element has auxiliary positioning and retaining means arranged at the front, in a number mating with the positioning and retaining means on the opposite side of the device according to the invention; in this embodiment the marker means may be included on the longitudinal element also.